ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 9

Document Title:

Supplementary External Dose Information 

for Rocky Flats Plant

Document Number: ORAUT-OTIB-0027

Revision: 00

Effective Date: 05/19/2005

Type of Document: OTIB

Supersedes: None

Subject Expert: Matthew H. Smith

Document Owner

Approval: Signature on File Approval Date: 05/16/2005

Steven E. Merwin, Principal External Dosimetrist

Approval: Signature on File Approval Date: 05/16/2005

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 05/16/2005

Richard E. Toohey, Project Director

Approval: Signature on File Approval Date: 05/19/2005

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE REPLACE THE PRIOR REVISION. 

PLEASE DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-OTIB-0027 Revision No. 00 Effective Date: 05/19/2005 Page 2 of 9

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

09/23/2004 00-A New document to establish Technical Information Bulletin for 

Supplementary External Dose Information for Rocky Flats Plant. 

Initiated by Matthew H. Smith.

02/08/2005 00-B Incorporates internal review comments. Initiated by Matthew H. 

Smith.

05/03/2005 00-C Incorporates NIOSH review comments. Initiated by Matthew H. 

Smith.

05/05/2005 00-D Incorporates additional NIOSH review comments. Initiated by 

Matthew H. Smith.

05/19/2005 00 First approved issue. No training required. Initiated by Matthew H. 

Smith.
Document No. ORAUT-OTIB-0027 Revision No. 00 Effective Date: 05/19/2005 Page 3 of 9

TABLE OF CONTENTS

Section Page

Acronyms and Abbreviations.................................................................................................................... 4

1.0 Scope............................................................................................................................................... 5

2.0 Estimating Relative Contributions from High, Medium, and Low-Energy 

Photons and Electrons from Reported Doses................................................................................. 5

3.0 Uncertainty....................................................................................................................................... 7

References................................................................................................................................................ 9

LIST OF TABLES

Table Page

2-1 Default photon energy distribution for RFP materials.................................................................. 5

4-1 RFP external dosimetry uncertainty values and correction multipliers........................................ 7

4-2 RFP external dosimetry claimant favorable uncertainty factors.................................................. 8
Document No. ORAUT-OTIB-0027 Revision No. 00 Effective Date: 05/19/2005 Page 4 of 9

ACRONYMS AND ABBREVIATIONS

cSv centisievert

DCF dose conversion factor

GM geometric mean

GSD geometric standard deviation

Hp(10) dose equivalent at a depth of 10 millimeters

IREP Interactive RadioEpidemiological Program

mrem millirem
Document No. ORAUT-OTIB-0027 Revision No. 00 Effective Date: 05/19/2005 Page 5 of 9

1.0 SCOPE

The purpose of this document is to supplement the information given in Technical Basis Document for 

Rocky Flats Plant – Occupational External Dosimetry (Rev 00),

1

 and Technical Basis Document for 

Rocky Flats Plant – Occupational External Dosimetry (Rev 01).2 Additional information is given for the 

following topics;

• Calculating dose from low-energy photons and electrons

• Dosimetry uncertainty values

2.0 ESTIMATING RELATIVE CONTRIBUTIONS FROM HIGH, MEDIUM, AND LOWENERGY PHOTONS AND ELECTRONS FROM REPORTED DOSES

As discussed in the RFP external TBD (ORAUT-TKBS-0011-6) low energy photons from plutonium 

are generally stopped by the metal sides of the glove boxes that the majority of the plutonium was 

handled in. However; low-energy photons that are for the most part shielded do, in fact, escape the 

glovebox through material release, open glove ports, non-leaded windows, and from oxide coated on 

the interior surfaces of the gloves, especially when they are pulled outside the glovebox for storage to 

prevent them from being caught in machinery (DOE 2003). To take credit for this type of exposure, 

25% of the photon exposure spectra from freshly separated plutonium is assumed to be from <30 keV 

photons. The default assumptions are shown in Table 2-1.

Table 2-1. Default photon energy distribution for RFP materials.

Energy Plutonium Enriched uranium Depleted uranium

<30 keV 25% 0% 0%

30-250 keV 75% 100% 50%

>250 keV 0% 0% 50%

To more accurately define the dose at Rocky Flats, various algorithms were applied to measured 

doses. To accurately define the various spectral components and their contribution to the dose, it is 

necessary to algebraically manipulate the reported skin and penetrating dose. In the discussion 

below “Skin” dose and “Pen” dose are the doses as reported for Rocky Flats workers.

Pre - 1960

The two-element film dosimeter used at RFP from prior to 1960 had both Open Window (OW) and 

cadmium (CD) filter components. Some dosimetry records indicate the dose determined by the film 

darkening under each dosimeter element, as well as the recorded skin and penetrating dose values.

Based on review of some of these data and data after 1960, the skin dose in this era was calculated 

as a sum of each of the three windows (OW + CD + BR).The dosimeter could not effectively measure 

the 60 keV photons, thus the reported penetrating (Pen) dose was calculated from the measured OW 

and CD component doses using the algorithm: Pen = 50% • OW + CD and the reported Skin dose 

was calculated as Skin= OW + CD. The addition of 50% of the recorded OW dose to the recorded 

CD dose was determined by Rocky Flats staff to correct the reported Pen dose for this 

underestimation (i.e. the relative ratio of the 60 keV photon dose to OW dose contribution is was 

determined to be about 0.5). 

Thus the sum of the low-energy (<30 keV photons or >15 keV electron) and the photon doses (30-250 

keV and/or >250 keV photons as applicable) exceeds the original reported skin dose. As a result, 

the following method should be used to estimate the low-energy photon dose for plutonium workers, 
Document No. ORAUT-OTIB-0027 Revision No. 00 Effective Date: 05/19/2005 Page 6 of 9

intermediate/high-energy photons for plutonium and uranium workers, as well as the >15 keV 

electrons for uranium workers: 

electrons>15 keV or photon<30 keV = [skin-pen]/0.50 = OW

photon(30 keV-250 keV ) + photon(>250 keV ) = pen = CD + 50%*OW

Using these equations and available knowledge of source material (e.g. plutonium, enriched or 

depleted uranium) spectra, an estimate of >15 keV electrons, <30 keV photons, 30-250 keV photons 

and >250 keV photon dose for use in dose reconstruction can be calculated from the reported Pen 

and Skin doses. Alternatively, if original component data is available in the dosimetry record, Pen and 

Skin doses can be calculated using the CD and OW results and the equations above. 

1960 - 1970

The three-element film dosimeter used at RFP from 1960 to 1969 also had an Open Window (OW), a 

cadmium (CD) filter, and an additional brass (BR) filter providing half the filtration of the CD. The 

brass filter was added to more accurately measure the 60 keV photons. This dosimeter was phased 

out during the year 1970.

Some dosimetry records (illustrated in Attachment A-7 of the External Dose TBD) indicate the dose 

determined by the film darkening under each dosimeter element, as well as the recorded skin and 

penetrating dose values. Based on review of some of these data, the skin dose in this era was 

calculated as a sum of each of the three windows (OW + CD + BR). The penetrating dose was 

calculated by adding the CD + BR + 35% • OW. The 35% OW addition to the deep dose was a DOE 

weapons complex standard practice during this time period (including Hanford and Savannah River) 

to account for some low-energy photon (<30 keV) contribution to deep dose.

To properly reconstruct the low-energy and intermediate-energy photon dose between 1960 and 

1970, the following reverse algorithm should be applied:

electrons>15 keV or photon<30 keV = [Skin-Pen]/0.65 =OW

photon(30 keV-250 keV ) + photon(>250 keV ) = Skin – (electrons>15 keV or photon<30 keV ) = BR + CD

Using these equations and available knowledge of source material (e.g. plutonium, enriched or 

depleted uranium) spectra, an estimate of >15 keV electrons, <30 keV photons, 30-250 keV photons 

and >250 keV photon dose for use in dose reconstruction can be calculated from the reported Pen 

and Skin doses. Alternatively, if original component data is available in the dosimetry record, Pen and 

Skin doses can be calculated using the CD, BR and OW results and the equations above. 

1970 - Present

Starting in 1970, RFP used TLDs to measure photon dose. The TLD materials used were much more 

tissue-equivalent and the response much less energy-dependent. Dosimeters were calibrated to 

more appropriate photon energies and filter design had advanced. It is believed that these 

dosimeters performed substantially better than film. Although various chip and filter combinations 

were used, data provided in DOE dosimetry files does not generally include dose from individual 

components similar to the CD, BR and OW categories from the film era. However, in order to avoid 

omission or over application of dose due to filter design, the following relationships should be used for 

this time period:

electrons>15 keV or photon<30 keV = Skin - Pen
Document No. ORAUT-OTIB-0027 Revision No. 00 Effective Date: 05/19/2005 Page 7 of 9

photon(30 keV-250 keV ) + photon(>250 keV ) = Pen

Using these equations and available knowledge of source material (plutonium, enriched or depleted 

uranium) spectra, an estimate of >15 keV electrons, <30 keV photons, 30-250 keV photons and >250 

keV photon dose for use in dose reconstruction can be calculated from the reported Pen and Skin 

doses.

3.0 UNCERTAINTY

The Technical Basis Document for Rocky Flats Plant Occupational External Dosimetry, (ORAUTTKBS-0011-6) provides estimates of the 95% upper confidence dose at various reported doses. 

Table 4-1 provides factors for dosimetry uncertainty for the variety of systems in use during operations 

at RFP. The factors are taken directly from tables provided in the TBD when available or calculated 

from upper 95% confidence dose provided. The estimated error factors are proportional to the 

individual dosimeter reading. Choice of a specifically applicable uncertainty will depend on the 

dosimeter result. Also provided in Table 4-1 are correction multipliers that apply to neutron dosimetry. 

These correction multipliers are provided for completeness but are not related directly to statistical 

uncertainty. Table 4-2 provides a claimant favorable interpretation of the more detailed information in 

Table 4-1 that is only related to Uncertainty Factors on the dosimeter response. 

Table 4-1. RFP external dosimetry uncertainty values and correction multipliers.

(Correction multipliers) Uncertainty factors

Dosimeter type Period

Unmonitored 

energies Building

Film reading 

bias LOD

Dosimeter result 

range (mrem)

Upper 95% confidence 

dose multiplier

Photon

Film 1951 - 1969 1 All 1 40 >LOD 1.2* reported dose

Loose-Chip TLD 1970 - 1982 1 All 1 20 >LOD to 100 2.0* reported dose

>100 1.26* reported dose

1983 - 1998 1 All 1 20 <2 1.00* reported dose

>2 1.23* reported dose

<2 1.00* reported dose

Panasonic TLD

1999 - 2003 1 All 1 10

>2 1.18* reported dose

Neutron

1951 - 1963 2.5 B-771 1.99 1.93* reported dose

Other neutron 

buildings

1.13

120-400 All until NDRP data

2.45* reported dose

B-771 1.99 1.93* reported dose

Film

1964 - 1970 1

Other neutron 

buildings

1.13

120-320 All until NDRP data

2.45* reported dose

Loose-Chip TLD 1971 - 1982 1 All 1 20 >5 1.20* reported dose

Panasonic TLD (initial 

algorithm)

1983 - 1990 1 All 1 32 >5 1.21* reported dose

Panasonic TLD 

(Sanford algorithm)

1991 - 1992 1 All 1 32 >5 1.14* reported dose

Panasonic TLD (1993 

updated algorithm)

1993 - 2003 1 All 1 15 >5 1.18* reported dose

Electron

Film 1951 – 1968 1 All 1 40 >LOD to 100 1.5* reported dose

>100 1.2* reported dose

Loose-Chip TLD 1969 - 1982 1 All 1 20 >LOD to 100 1.5* reported dose

>100 1.26* reported dose

All years 

(1983-2003)

<2 1.19 (2 rem), 1.14 

(1rem)

1983-1989 18 >2 1.12* reported dose

1990-1992 80 >2 1.12* reported dose

Panasonic TLD

1993 – 2003

1 All 1

15 >2 1.12* reported dose
Document No. ORAUT-OTIB-0027 Revision No. 00 Effective Date: 05/19/2005 Page 8 of 9

Table 4-2. RFP external dosimetry claimant favorable uncertainty factors.

Dosimeter type Period Building

Uncertainty factor to estimate claimant 

favorable upper 95% confidence dose

Photon

Film 1951 - 1969 All 1.20

Loose-Chip TLD 1970 - 1982 All 2.0 (1.26)a

Panasonic TLD 1983 - 1998 All 1.23

Neutron

Film 1951 - 1970 B-771 1.93

Other neutron buildings 2.45

Loose-Chip TLD 1971 - 1982 All 1.21

Panasonic TLD (initial algorithm) 1983 - 1990 All 1.21

Panasonic TLD (Sanford algorithm) 1991 - 1992 All 1.21

Panasonic TLD (1993 updated algorithm) 1993 - 2003 All 1.21

Electron

Film 1951 – 1968 All 1.5

Loose-Chip TLD 1969 - 1982 All 1.5

Panasonic TLD All years (1983-2003) All 1.19

a. If all individual dosimeter readings are over 100 mrem, then the lower factor of 1.26 can be used.
Document No. ORAUT-OTIB-0027 Revision No. 00 Effective Date: 05/19/2005 Page 9 of 9

REFERENCES

1. ORAUT-TKBS-0011-6, Technical Basis Document for Rocky Flats Plant Occupational External 

Dosimetry, Rev 00, January, 2004. 

2. ORAUT-TKBS-0011-4, Technical Basis Document for Rocky Flats Plant-Occupational 

Environmental Dose, Rev 01, June 29, 2004.

3. DOE (U.S. Department of Energy), 2003, Guide of Good Practices for Occupational Radiological 

Protection in Plutonium Facilities, DOE-STD-1128-98, Reaffirmation with Errata.